The linear polarisation planes (defined as X and Y and orthogonal to each other) of most of the Eutelsat satellites are not parallel/orthogonal to the equatorial plane. For historical reasons, the polarisation planes are inclined by an angle with respect to the equatorial plane. This angle is referenced as the polarisation skew.

This value is of fundamental importance for the following types of antennas, whenever the polarisation alignment is performed in open loop (calculated):

• Earth Stations on Vessels (ESVs)

• Satcom-On -The Move (SOTM)

• Auto-pointing antennas

If the pointing and polarisation alignment software of an antenna falling in the categories above did not take duly into account this value of skew, the polarisation discrimination achieved at the end of the alignment would suffer a major degradation with respect to the value which the antenna optics could theoretically yield, with a consequent high risk of interference to other services on the opposite polarisation and the achievable performance would not be met.

The reference X-polarisation is defined as that polarisation whose plane makes an angle of 93.535° in an anti-clockwise direction, looking towards the earth, about a reference vector with respect to a plane containing this vector and the pitch axis.
The reference vector is defined as the vector from the satellite in the direction 0.21° towards west and 6.07° towards north in satellite coordinates.

The reference Y-polarisation is defined as that polarisation whose plane is orthogonal to the Xpolarisation< plane and the reference vector defined above.

In other words the skew of the Eutelsat satellites is +3.535°, clockwise when looking at the satellite from the earth, from anywhere on the meridian (in the northern hemisphere) corresponding to the orbital location of the satellite.

In the southern hemisphere the skew of the Eutelsat satellites is +183.535°, clockwise, from anywhere on the meridian corresponding to the orbital location of the satellite.

There are several satellites of the Eutelsat fleet using linear polarisation which are an exception.

An ESVA is necessary in order to verify the antenna performance, i.e. the off axis radiation, the cross-polar discrimination Transmit and Receive gain, G/T, maximum EIRP capability.

It is mandatory for antennae with a large dish size.

Minimum requirements for the correct performance of the ESVA are that the antenna should be motorised in Azimuth and Elevation. Nevertheless, ESVA tests can be performed on any type of earth station. In the case of non-motorised antennae, necessary arrangements can be made to enable the angular read-out of the antenna.

Once the performance has been verified and considered acceptable, a certificate of earth station performance granting indefinite and unconditioned access will be delivered to the earth station owner.

If the performance is not acceptable, either the test must be repeated after the necessary adjustments have been made to the antenna, or some limitations will be enforced (typically on the maximum allowed transmit EIRP and also on the duration of the approval).

To find out more, or to arrange for an ESVA test, contact Messrs F.Schurig or K.Badalov
+33 1 5398 4825 or + 33 1 53984976.

The Initial Full Line-Up (Digital Line-up) is strongly recommended for all earth stations transmitting digital signals (digital TV broadcasting, Internet backbone, SNGs etc), but it is not mandatory. This test verifies the whole earth station performance (whereas the ESVA verifies only the antenna performance), including the base-band equipment (i.e. modems, multiplexers).

To find out more, or to arrange for the performance of a digital line-up, contact the earth station approval office (+33 1 5398 4613 or + 33 1 5398 4816) or the ERS (+43 59 059 3 47201).

ESVA tests are a very cost efficient means to test an earth station and to ensure that the antenna manufacturer specifications are being met.

By checking the off-axis radiation, Eutelsat ensures that, when transmitting, the earth station antenna will not interfere with other carriers transmitted on satellites adjacent to the satellite being accessed.

By checking the cross-polar performance, Eutelsat ensures that the earth station antenna will not interfere with other services carried on a transponder cross-polar to the one being accessed by the earth station.

Moreover, the transmit antenna gain and G/T can be precisely measured. The ESVA test enables the earth station operator to calibrate the transmit and receive chains and to determine the exact earth station transmit EIRP as well as the maximum earth station EIRP capability.

With the assistance of the Eutelsat Reference Station, the Station Under Test can be properly aligned and therefore prepared for the operational traffic.

A fee of 3000€ for up to 10hrs testing, applies to earth stations that commence a chargeable EUTELSAT service within 8 months of the ESVA completion. Additional hours (and hours started) are charged at 600€. Considerably higher rates apply to stations that do not operate within EUTELSAT networks.

The approval to access the Eutelsat space segment stipulates the maximum allowable EIRP density at beam edge (i.e. at the satellite receive contour of 0 dB/K). This specific EIRP density is also known as EIRP0 density. The EIRP0 density can be either referred to 4 KHz or 40 KHz band, its measurement unit is expressed in dBW/4 KHz or in dBW/40 KHz.

Yes, access to the Eutelsat space segment is not restricted to type approved antennas only.

There are three types of antenna:

Type approved, which have undergone a long process of verification and testing, often witnessed by Eutelsat and/or other satcom operators. Individual verification is not required for this type of antennae.

Individually approved, which are not type approved but whose performance is known to Eutelsat and for which individual verification is not strictly mandatory. Eutelsat, however, reserves the right to instigate the performance of verification tests at any time should problems occur.

Other antennas not falling into any of the categories above and for which individual verification of the performance is required.

Yes. However VSAT networks usually comprise hundreds or even thousands of VSATs. Therefore in order to roll out a large VSAT network on the Eutelsat space segment it is strongly recommended in order to pro-actively avoid interferences to other services, that the VSATs be type approved and if this is not the case, that the VSATs to be deployed be fully characterized and measurements results be made available to Eutelsat.